In conventional cartridges mountable in a liquid ejecting device that supply liquid to the liquid ejecting device, Japanese Patent Application Publication No. 2004-34406 discloses a liquid cartridge that can detect amounts of liquid left in the liquid cartridge in multiple stages. This reference includes a detection member in the liquid cartridge. An end of the detection member is rotatably supported, while the other end the detection member is floating on the surface of the liquid accommodated in the liquid cartridge. As the amount of the liquid in the liquid cartridge decreases, the detection member rotationally moves about the one end thereof. As the detection member rotationally moves, length of an area floating above the liquid surface in the detection member changes when seen from above. This patent reference employs an optical sensor for measuring, from the above, the length of the area of the detection member floating above the liquid surface, and detects how much liquid remains in the liquid cartridge in a phased manner according to the measured length.
According to this reference, however, the length of the floating area above the liquid surface in the detection member is necessary to be measured. On the other hand, an area that the optical sensor can detect is limited, and therefore, if the length of the area that the optical sensor can measure is beyond the detectable area, the optical sensor needs to be relocated relative to the detection member in order to perform measurement as disclosed in this reference. Hence, in the liquid ejecting device that can mount liquid cartridges disclosed in this reference, a device for relocating the optical sensor relative to the liquid cartridge is necessary to be provided, leading to an increase in costs of the liquid ejecting device.